Not Applicable
The present invention relates in general to rotary cutting machines such as drill presses, milling machines, and the like, and in particular to a vibration-dampened spindle and tool holder assembly employing a resilient dampening member in compressed interfacing contact between the spindle and tool holder and encapsulated from the environment to thereby maintain generally non-contaminated and non-adulterated dampening properties.
A rotary cutting machine typically includes a motor-rotated spindle to which a tool holder is proximally attached and from whose distal end a held cutting tool projects for cutting contact with a workpiece. Attachment of the tool holder to the spindle generally is accomplished by providing a cavity in the spindle into which the proximal end of the tool holder is secured as with a centrally disposed threaded bolt. While slower rotational speeds generally permit the cutting machine to perform adequately, high speed cutting, which is, of course, preferred, can cause substantial difficulty in producing a satisfactory work product. In particular, at least two major factors can preclude satisfactory operations. The first of these factors concerns the development of vibratory forces that occur between the spindle and the tool holder. Specifically, at higher rotational cutting speed, the cutting tool begins to chatter or vibrate such that adequate tool control cannot be maintained and damage to the workpiece, along with potential injury to the operator should runaway control occur, can realistically occur. The second such major factor that can contribute toward unsatisfactory operations occurs as the cutting tool is used and dirt, metal shavings, and other contaminants of the environment reach interface sites of the spindle and tool holder to cause interference with concentric alignment of cutting heads in relation to cutting sites because of imbalances caused by particulate becoming lodged in a non-concentric manner.
In view of these difficulties, it is therefore apparent that needs are present to, first, stabilize high speed operation of rotary cutting tools by dampening vibrations and, second, maintain tool cleanliness at critical sites thereof such that concentricity as well as stability are preserved. Accordingly, a primary object of the present invention is to provide a vibration-dampened spindle and tool holder assembly for a rotary cutting machine whereby vibration dampening material is strategically placed to promote vibration-free operability.
Another object of the present invention is to provide an accommodation site for dampening material where the dampening material is protected from contamination generated in the work environment.
These and other objects of the present invention will become apparent throughout the description thereof which now follows.
The present invention is a vibration dampened tool-holder mount and holder assembly for a rotary cutting machine. The assembly includes a tool-holder mount, such as exemplified by a spindle, for retaining a tool holder, and is provided with an axial recess with a distal entrance. Also included as a component of the assembly is a tool holder having a proximal end for retention within the recess of the tool-holder mount and an interfacing ledge immediately distal from this proximal end. The ledge has a top surface with a distal parameter portion for abutment with a tool-holder mount surface surrounding the entrance to the recess thereof, and a continuous channel disposed in a proximal portion of the top surface. A resilient dampening member is disposed in the channel and sized to at least fill the channel to provide an exposed top for compressed abutment with the tool-holder mount surface. This dampening member preferably is fabricated from a natural or synthetic rubber composition, and is formed to have either a rectangular or a circular cross sectional configuration. Because the dampening member is situated within the channel as defined above, the interfacing connection of the tool-holder mount and the tool holder permits the outer parameters of the mount surface itself and tool holder itself to meet while the dampening member is enshrouded by these meeting parameters and thereby protected from contaminant entry during compression-relaxation activity during its dampening action. Additionally, such dampening-member placement aids in ensuring a simultaneous concentrical fit of the mount and the tool holder to thereby produce a predictable and focused precise-rotation presence for workpiece production.